Dlc film coated plastic container, and device and method for manufacturing the plastic container

ABSTRACT

The present invention provides method of DLC film coating a plastic container by DLC film coating the container in an apparatus, where the apparatus comprises a container side electrode which forms one portion of a pressure-reducing chamber and a facing electrode, where the container side electrode is formed so that the average inner hole diameter (R 2 ) of the inner wall surrounding a neck portion is smaller than the average inner hole diameter (R 1 ) of the inner wall surrounding the body portion, and the average distance (d 2 ) between the outer wall of the container and the inner wall of the container side electrode in a horizontal cross section with respect to the vertical direction of the container at the neck portion becomes longer than the average distance (d 1 ) between the outer wall of the container and the inner wall of the container side electrode.

TECHNOLOGICAL FIELD

The present invention is related to a plastic container having an innerwall surface coated with a diamond like carbon (DLC) film, amanufacturing method thereof and a manufacturing apparatus therefor.

PRIOR ART TECHNOLOGY

Japanese Laid-Open Patent Application No. HEI 8-53117 discloses anapparatus for manufacturing a carbon film coated plastic container whichcoats the inner wall surface of the plastic container with a carbonfilm, and a manufacturing method thereof. As shown in FIG. 11, thisapparatus is equipped with a hollow external electrode 112 which isformed to house a container and includes a space having a shape roughlysimilar to the external shape of the housed container 120, an insulatingmember 111 which insulates the external electrode and makes contact witha mouth portion of the container when the container is housed inside thespace of the external electrode, a grounded internal electrode 116 whichis inserted into the inside of the container housed inside the space ofthe external electrode from the mouth portion 120A of the container,exhaust means 115 which communicate with the inside of the space of theexternal electrode to exhaust the inside of the space, supply means 117which supply a source gas to the inside of the container housed insidethe space of the external electrode, and a high frequency power source(RF power source) 114 which is connected to the external electrode.

The manufacturing method of the same laid-open patent application formsa carbon film by a plasma CVD method which generates plasma between theexternal electrode and the internal electrode in the same apparatus.Namely, in the method of manufacturing a carbon film coated plasticcontainer, a space having a shape roughly similar to the external shapeof a housed container is formed in the external electrode, the externalelectrode is insulated by an insulating member which makes contact withthe mouth portion of the container housed inside this space, an internalelectrode is inserted into the inside of the container housed inside thespace from the mouth portion of the container and this internalelectrode is grounded, the inside of the space of the external electrodeis exhausted, a source gas is supplied to the inside of the containerhoused inside the space of the external electrode, and then a highfrequency is applied to the external electrode.

SUMMARY OF THE INVENTION

According to research conducted by the inventors of the presentinvention, a DLC film coated plastic container manufactured byelectrodes similar to those disclosed in the laid-open patentapplication described above had a satisfactory oxygen barrier property(the oxygen permeability was reduced to less than one tenth compared tothe base material) but the color of the neck portion was dark. Further,when the container was recycled, there were cases where the colorationof the neck portion caused problems such as coloration of the recycleditems.

In the laid-open patent application described above, plasma is createdafter a prescribed film forming pressure is achieved by balancing theexhaust of the inside of the space housing the plastic container and thesupply of source gas to the inside of the plastic container.Accordingly, when plasma is created and before and after this, thesource gas normally flows through the inside of the plastic container,and this forms a source gas flux. In the case where a container having acontainer shape in which the neck portion is narrow relative to the bodyportion is made the object, the cross-sectional area of a horizontalcross section at the neck portion of the container with respect to acentral axis of the vertical direction of the container becomes smallersuddenly compared to the body portion. Due to this kind of suddendecrease of cross-sectional area, the present inventors discovered thatthe gas pressure of the source gas flowing through the inside of thecontainer rises at the neck portion which causes the plasma density toalso rise. In this way, because the DLC film formed on the inner wallsurface of the neck portion of the container exposed to high densityplasma receives more plasma damage or a stronger plasma etching effect,there is considerably more coloring of dark yellowish brown at the neckportion than there is at the body portion.

In this regard, it is an object of the present invention to provided anapparatus for manufacturing a DLC film coated plastic container whichhas the same degree of oxygen barrier property as a prior art DLC filmcoated plastic bottle, and can prevent the coloring of the DLC filmformed on the neck portion of the container. Namely, it is an object tomitigate plasma damage or plasma etching of the DLC film at the neckportion by adjusting the relationship between the space (neck portionoffset distance) between the container outer wall at the neck portion ofthe container and the container side electrode inner wall and the space(body portion offset distance) between the container outer wall at thebody portion of the container and the container side electrode innerwall under conditions in which a desired oxygen barrier property isobtained. Further, it is an object to prevent irregular color of thecontainer and solve recycling problems due to the coloring describedabove by providing a manufacturing apparatus that makes it possible toform a transparent film roughly the same as that of the body portion onthe neck portion. Further, by adjusting the neck portion offset distanceand the body portion offset distance, it is possible to prevent theoccurrence of irregular color in the rotation direction of the containercentral axis.

Further, it is an object of the present invention to regulate the neckportion offset distance in more detail in the manufacturing apparatusaccording to the present invention. Namely, an optimum neck portionoffset is regulated with the plasma density distribution, the oxygenbarrier property (oxygen permeability) or the coloration degree of thecontainer as an indicator.

Further, it is an object of the present invention to provide amanufacturing apparatus which has a container side electrode having aninner wall structure suited to a container having an axial symmetricalshape with respect to the central axis of the vertical direction of thecontainer. At this time, combined concrete and simple shapes of theinner wall structure of the container side electrode are proposed.

Further, it is an object of the present invention to propose combinedconcrete and simple shapes of the inner wall structure of an optimumcontainer side electrode for containers having an angular tube-shapedbody portion.

Further, it is an object of the present invention to concretely regulatethe body portion offset distance for obtaining a container colorationdegree (which changes depending on plasma density distribution shiftsand the like) below a prescribed value, and a required oxygen barrierproperty in the manufacturing apparatus according to the presentinvention.

Further, as an object of both securing a required oxygen barrierproperty and preventing coloration, it is an object of the presentinvention to provide a plurality of manufacturing methods which preventcoloration of the container by controlling the increase of source gaspressure inside the container at the neck portion so as to form auniform plasma density distribution. Further, it is an object of thepresent invention to also propose an optimum manufacturing apparatuswhen executing these manufacturing methods.

Further, it is an object of the present invention to provide amanufacturing apparatus which solves the problems described above and atthe same time makes it possible to prevent the adherence of dust to asource gas inlet pipe.

Further, it is an object of the present invention to provide an optimummanufacturing method and an optimum manufacturing apparatus formanufacturing containers for beverages.

In this way, it is an object of the present invention to provide arecyclable plastic container which has an oxygen gas barrier propertyand can prevent coloration of the neck portion.

An apparatus for manufacturing a DLC film coated plastic containeraccording to the present invention includes a container side electrodewhich forms one portion of a pressure-reducing chamber which houses acontainer formed from plastic in which the cross-sectional area of anopening of said container is made smaller than the cross-sectional areaof a horizontal cross section at a body portion of said container and aneck portion is provided between said opening and said body portion, anda facing electrode which faces said container side electrode and isarranged inside said container or above said opening, wherein saidcontainer side electrode and said facing electrode are made to face eachother via an insulating body which forms a portion of saidpressure-reducing chamber, source gas supply means which supply a sourcegas that is converted to plasma for coating the inner wall surface ofsaid container with a diamond like carbon (DLC) film includes a supplygas inlet pipe provided in said pressure-reducing chamber to introducesaid source gas supplied to said pressure-reducing chamber to the insideof said container, exhaust means which exhaust gas inside saidpressure-reducing chamber from above the opening of said container areprovided, and high frequency supply means which supply a high frequencyis connected to said container side electrode, wherein said containerside electrode is formed so that the average inner hole diameter (R2) ofthe inner wall surrounding said neck portion when the container ishoused becomes smaller than the average inner hole diameter (R1) of theinner wall surrounding said body portion, and the average distance (d2)between the outer wall of said container and the inner wall of saidcontainer side electrode in a horizontal cross section with respect tothe vertical direction of said container at said neck portion becomeslonger than the average distance (d1) between the outer wall of saidcontainer and the inner wall of said container side electrode in ahorizontal cross section with respect to the vertical direction of saidcontainer at said body portion.

In the apparatus for manufacturing a DLC film coated plastic containerdescribed in claim 1, preferably said average distance d2 is formed tobe a distance which suppresses the rise in plasma density accompanyingthe rise in pressure of the source gas converted to plasma at said neckportion inside said container in order to form a roughly uniform plasmadensity inside said container.

In the apparatus for manufacturing a DLC film coated plastic containerdescribed in claim 1, preferably said average distance d2 is formed tobe the same as or shorter than the distance at which the strength ofionic impacts due to collisions of the ions of the source gas convertedto plasma with the inner wall surface of said container forms an ionicimpact strength capable of forming a DLC film having a prescribed lowerlimit oxygen barrier property, and said average distance d2 is formed tobe the same as or longer than the distance at which the entire wallsurface of said container has a roughly uniform color by suppressingcoloration of a specific part of said container from said neck portionto said opening caused by plasma damage or plasma etching of the innerwall surface of said container due to the increase in plasma densityaccompanying the increase in pressure of the source gas converted toplasma in said neck portion inside said container.

In the apparatus for manufacturing a DLC film coated plastic containerdescribed in claim 1, preferably said average distance d2 is formed tobe a distance at which the DLC film coated plastic container secures aprescribed oxygen barrier property and the entire wall surface of saidDLC film coated plastic container has a roughly uniform color.

In the apparatus for manufacturing a DLC film coated plastic containerdescribed in claim 1, preferably the average diameter of said bodyportion of said container is made D1, the average diameter of said neckportion is made D2, and in the case where K is made an offsetcoefficient that satisfies the relationship of Equation 1, the offsetcoefficient K satisfies the relationship of Equation 2 or Equation 3,and said average distance d2 forms the d2 determined from Equation 1.

d2=K×(D1−D2)/2+d1  (Equation 1)

0.29≦K≦0.79 where 0.2 mm≦d1≦2.0 mm  (Equation 2)

0.11≦K≦0.51 where 2.0 mm<d1≦4.0 mm  (Equation 3)

In the apparatus for manufacturing a DLC film coated plastic containerdescribed in claim 1, preferably the average diameter of said bodyportion of said container is made D1, the average diameter of said neckportion is made D2, an offset coefficient that satisfies therelationship of Equation 4 is made K, and when a of Equation 4 is acontainer compensation coefficient that takes into account the containershape dependency satisfying Equation 5, the offset coefficient Ksatisfies the relationship of Equation 2 or Equation 3, and said averagedistance d2 forms the d2 determined from Equation 4.

d2=αK×(D1−D2)/2+d1  (Equation 4)

α=(D1/D2)²/3.54  (Equation 5)

In the apparatus for manufacturing a DLC film coated plastic containerdescribed in claim 1, 2, 3, 4, 5 or 6, preferably said container has anaxial symmetrical shape with respect to the central axis of the verticaldirection, and the inner wall shape of said container side electrode isformed to be an axial symmetrical shape with respect to said centralaxis when said container is housed.

In the apparatus for manufacturing a DLC film coated plastic containerdescribed in claim 1, 2, 3, 4, 5, 6 or 7, preferably when said containeris housed in said container side electrode, the inner wall of saidcontainer side electrode surrounding said body portion of said containeris formed to have a cylindrical shape, the inner wall of said containerside electrode surrounding said neck portion of said container is formedto have a truncated cone shaped cylindrical shape in which the diameterbecomes smaller toward the container opening, and the inner wall of saidcontainer side electrode is formed to have a continuous shape that doesnot have different stages.

In the apparatus for manufacturing a DLC film coated plastic containerdescribed in claim 8, preferably the inner wall of said container sideelectrode surrounding the opening of said container is formed to have acylindrical shape.

In the apparatus for manufacturing a DLC film coated plastic containerdescribed in claim 1, 2, 3, 4, 5 or 6, preferably said body portion ofsaid container has a square tube shape, the inner wall of said containerside electrode surrounding said body portion of said container is formedto have a square tube shape, the inner wall of said container sideelectrode surrounding said neck portion of said container is formed tohave a truncated pyramid shaped square tube shape in which the diameterbecomes smaller toward the container opening, a square tube shape or ashape which is a combination of these, and the inner wall of saidcontainer side electrode is formed to have a continuous shape that doesnot have different stages.

In the apparatus for manufacturing a DLC film coated plastic containerdescribed in claim 10, preferably the inner wall of said container sideelectrode surrounding the opening of said container is formed to have asquare tube shape.

In the apparatus for manufacturing a DLC film coated plastic containerdescribed in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11, preferably saidcontainer side electrode is formed so that d1 is greater than 0 mm andless than or equal to 4 mm.

Further an apparatus for manufacturing a DLC film coated plasticcontainer according to the present invention includes a container sideelectrode which forms one portion of a pressure-reducing chamber whichhouses a container formed from plastic, and a facing electrode whichfaces said container side electrode and is arranged inside saidcontainer or above said opening, wherein said container side electrodeand said facing electrode are made to face each other via an insulatingbody which forms a portion of said pressure-reducing chamber, source gassupply means which supply a source gas that is converted to plasma forcoating the inner wall surface of said container with a DLC filmincludes a supply gas inlet pipe provided in said pressure-reducingchamber to introduce said source gas supplied to said pressure-reducingchamber to the inside of said container, exhaust means which exhaust gasinside said pressure-reducing chamber from above the opening of saidcontainer are provided, and high frequency supply means which supply ahigh frequency is connected to said container side electrode, whereinexhaust conductance adjustment means are provided to carry outadjustment by freely restricting the amount of gas exhaust that isexhausted from a horizontal cross section of said pressure-reducingchamber above the opening of said container.

In the apparatus for manufacturing a DLC film coated plastic containerdescribed in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13,preferably said container is a container for beverages.

Further a method of manufacturing a DLC film coated plastic containeraccording to the present invention includes the steps of exhausting theinside of a container formed from plastic to a pressure less than orequal to a prescribed pressure, then introducing a source gas which willbe converted to plasma to the inside of said container while continuingto exhaust the inside of said container so that the inside of saidcontainer is replaced with said source gas and a prescribed equilibriumpressure is formed inside said container, then stopping most of theexhaust of the inside of said container and making the introduction rateof said source gas smaller than the introduction rate at the time ofreplacement so that the flow of said source gas inside said container isslowed and the pressure distribution inside said container is maderoughly uniform, and then generating source gas type plasma inside saidcontainer to form a DLC film on the inner wall surface of said plasticcontainer.

Further, a method of manufacturing a DLC film coated plastic containeraccording to the present invention includes the steps of exhausting theinside of a container formed from plastic to a pressure less than orequal to a prescribed pressure, then making the exhaust rate inside saidcontainer smaller or zero and introducing a source gas which will beconverted to plasma to the inside of said container, and then generatingsource gas type plasma inside said container to form a DLC film on theinner wall surface of said plastic container at the point in time whenthe pressure distribution inside said container is roughly uniform and aprescribed pressure has been reached.

In the method of manufacturing a DLC film coated plastic containerdescribed in claim 15 or 16, preferably said container is a containerfor beverages.

A DLC film coated plastic container according to the present inventionis a plastic container having a DLC film formed on the inner wallsurface thereof in which the cross-sectional area of an opening of saidcontainer is made smaller than the cross-sectional area of a horizontalcross section at a body portion of said container and a neck portion isprovided between said opening and said body portion, wherein the DLCfilm formed on said neck portion has a lower graphite mixing proportionthan the DLC film formed on said body portion, and the oxygenpermeability of said container is less than or equal to 0.0050ml/container (500 ml PET container)/day (23° C. and RH90%, measurementvalues after 20 hours from the start of nitrogen gas replacement). Atthis time, preferably the amount of graphite mixing of the DLC filmformed on said neck portion is 5˜18% of the amount of graphite mixing ofsaid body portion. In this regard, the amount of mixing is compared forthe same film thickness.

Further, the oxygen permeability of the container is given for a 500 mlcontainer prescribed as a standard, but this can be applied tocontainers having other capacities by carrying out ratio conversion. Forexample, in a 1000 ml container, oxygen permeability is less than orequal to 0.0100 ml/container/day.

Further, a DLC film coated plastic container according to the presentinvention is a plastic container having a DLC film formed on the innerwall surface thereof in which the cross-sectional area of an opening ofsaid container is made smaller than the cross-sectional area of ahorizontal cross section at a body portion of said container and a neckportion is provided between said opening and said body portion, whereinthe DLC film formed on said neck portion has a higher hydrogen atomcontent than the DLC film formed on said body portion, and the oxygenpermeability of said container is less than or equal to 0.0050ml/container (500 ml PET container)/day (23° C. and RH90%, measurementvalues after 20 hours from the start of nitrogen gas replacement). Atthis time, preferably the composition proportion of carbon and hydrogen(carbon atom/hydrogen atom) of the DLC film formed on said neck portionis 37/63˜48/52, and the composition proportion of carbon and hydrogen(carbon atom/hydrogen atom) of the DLC film formed on said body portionis 55/45˜75/25.

Further, a DLC film coated plastic container according to the presentinvention is a plastic container having a DLC film formed on the innerwall surface thereof in which the cross-sectional area of an opening ofsaid container is made smaller than the cross-sectional area of ahorizontal cross section at a body portion of said container and a neckportion is provided between said opening and said body portion, whereinthe DLC film formed on said neck portion has a lower graphite mixingproportion and a higher hydrogen atom content than the DLC film formedon said body portion, and the oxygen permeability of said container isless than or equal to 0.0050 ml/container (500 ml PET container)/day(23° C. and RH90%, measurement values after 20 hours from the start ofnitrogen gas replacement). At this time, preferably the amount ofgraphite mixing of the DLC film formed on said neck portion is 5˜18% ofthe amount of graphite mixing of said body portion, the compositionproportion of carbon and hydrogen (carbon atom/hydrogen atom) of the DLCfilm formed on said neck portion is 37/63˜48/52, and the compositionproportion of carbon and hydrogen (carbon atom/hydrogen atom) of the DLCfilm formed on said body portion is 55/45˜75/25.

In the apparatus for manufacturing a DLC film coated plastic containerof the present invention, it is possible to prevent coloration of theDLC film at the neck portion of a container manufactured to have thesame level of oxygen barrier property as a prior art DLC film coatedplastic bottle. This is achieved by adjusting the relationship betweenthe neck portion offset length and the body portion offset length tomitigate plasma damage or plasma etching of the DLC film at the neckportion. In this way, irregular color of the container can be preventedby forming a transparent film roughly the same as that of the bodyportion on the neck portion, and this makes it possible to solve therecycling problem due to coloration.

Further, in the present invention, an optimum offset is determined byindicating the plasma density distribution, the oxygen barrier property(oxygen permeability) or the coloration level of the container.

Further, the present invention shows concrete and simple embodiments ofa manufacturing apparatus suited to a container having an axialsymmetrical shape with respect to the central axis of the verticaldirection of the container or a container having a square tube shapedbody portion. In this way, instead of preparing a separate containerside electrode to match each of the various shapes of beveragecontainers, for example, the container side electrode can be used forall applications.

The present invention concretely shows the body portion offset length inthe manufacturing apparatus according to the present invention, and inthis way a container coloration level at or below a prescribed value anda required oxygen barrier property were obtained.

Further, in the manufacturing method of the present invention,coloration of the container is prevented by suppressing the rise insource gas pressure at the neck portion inside the container andcarrying out control so that the plasma density distribution becomesuniform, whereby both a required oxygen barrier property is secured andcoloration is prevented. Further, the present invention proposes anoptimum manufacturing apparatus when this manufacturing method iscarried out.

Further, the present invention is designed to solve the problemsdescribed above and at the same time prevent the adherence of dust tothe source gas inlet pipe.

Further, because both an oxygen barrier property and transparency areobtained, the present invention is ideally suited to the manufacture ofbeverage containers which require transparency and recyclability.

Further, the DLC film of the container manufactured by the apparatus ofthe present invention is a fine DLC film having a small number ofgraphite like carbon sp² bonding structures and a high proportion of sp³bonding structures (diamond structures and the like). This DLC filmmakes it possible to achieve a light uniform color over the entirecontainer while securing an oxygen barrier property.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing which shows one embodiment of the presentmanufacturing apparatus.

FIG. 2 is a drawing which shows the meaning of the symbols in thepresent invention.

FIG. 3 is a schematic drawing which shows a second embodiment of thepresent manufacturing apparatus.

FIG. 4 is a schematic drawing which shows a third embodiment of thepresent manufacturing apparatus.

FIG. 5 is a schematic drawing which shows another embodiment of a sourcegas inlet pipe in the apparatus of FIG. 1.

FIG. 6 is a schematic drawing which shows another embodiment of a sourcegas inlet pipe in the apparatus of FIG. 3.

FIG. 7 is a conceptual drawing which shows the flow of gas from thecontainer opening to the exhaust port using the apparatus of FIG. 3 asan example.

FIG. 8 is a drawing which shows the names of each part of a beveragecontainer.

FIG. 9 is a schematic drawing of an apparatus in the case where exhaustconductance adjustment means are provided using the apparatus of FIG. 3as an example.

FIGS. 10( a)˜10(c) are conceptual drawings which show details of theexhaust conductance adjustment means, wherein FIG. 10( a) is a schematicdrawing showing one embodiment of the exhaust conductance adjustmentmeans 50 in a cross section taken in the plane formed by the axialdirection of the source gas inlet pipe 9 and the insertion direction ofa restrictor 51 of the exhaust conductance adjustment means 50. FIG. 10(b) is a cross-sectional schematic drawing taken along X-X in FIG. 9, andis the case where the restrictor 51 is open. FIG. 10( c) is across-sectional schematic drawing taken along X-X in FIG. 9, and is thecase where the restrictor 51 is closed.

FIG. 11 is a drawing which shows a conceptual drawing of a prior artapparatus for manufacturing a DLC film coated plastic container.

FIG. 12 is a schematic drawing of the case where the container sideelectrode is given an electrode structure having a shape similar to thecontainer in the apparatus of FIG. 1.

FIG. 13 is a graph which shows the body portion offset length dependenceof the oxygen permeability.

FIG. 14 is a graph which shows the neck portion offset length dependenceof the oxygen permeability.

FIG. 15 is a graph which shows the body portion offset length dependenceof the b* value.

FIG. 16 is a graph which shows the neck portion offset length dependenceof the b* value.

FIG. 17 is a drawing which shows the relationship of the optimum offsetlength.

FIG. 18 is a picture which shows a comparison of a DLC film container(mentioned as present invention) obtained by the manufacturing apparatusof the present invention and a DLC film container obtained by a priorart manufacturing apparatus in which the inner wall of the space of thecontainer side electrode housing the container has a shape similar tothe container outer wall.

FIG. 19 is a drawing which shows the relationship between the filmthickness of the DLC film and the b* value.

FIG. 20 is a graph which shows the difference in transmittance spectrumproperties of DLC film containers which depend on the electrodestructure.

FIG. 21 is a graph which shows a comparison of the Raman spectrums ofthe container of the present invention and the container of ComparativeExample 2 (prior art technology).

FIG. 22 shows enlarged views of the DLC related portions after theeffects due to fluorescence are eliminated in FIG. 21.

FIG. 23 is a drawing which shows the sequence of Manufacturing Method 3.

FIG. 24 is a schematic drawing of the case where the container sideelectrode is given an electrode structure having a shape similar to thecontainer in the apparatus of FIG. 4.

The meaning of the symbols is as follows. 1 shows an upper electrode, 2shows a lower electrode, 3 shows a container side electrode, 4 shows aninsulating body, 5 shows a facing electrode, 5 a shows a tubular body, 5b shows a tubular body end, 5 c shows an internal electrode, 6 shows apressure-reducing chamber, 7 shows a plastic container, 8 shows anO-ring, 9 shows a source gas inlet pipe, 9 a shows a blowout hole, 10shows an opening, 11 shows an annular portion of the facing electrode,12 shows a matching box, 13 shows a high frequency power source, 14shows high frequency supply means, 16 shows a pipeline, 17 shows asource gas generating source, 18 shows source gas supply means, 19 showsa vacuum valve, 20 shows an exhaust pump, 21 shows exhaust means, 23shows an exhaust port, 50 shows exhaust conductance adjustment means, 51shows a restrictor, 52 shows a through hole, and 53 shows a restrictoropening/closing mechanism.

PREFERRED EMBODIMENTS OF THE INVENTION

Detailed descriptions showing embodiments of the present invention aregiven below, but it should not be interpreted that the present inventionis limited to these descriptions.

First, the structure of an apparatus for manufacturing a DLC film coatedplastic container according to the present invention will be describedwith reference to FIGS. 1˜12. Further, the same symbols are used for thesame members in the drawings. FIG. 1 is a schematic drawing showing oneembodiment of the present manufacturing apparatus. FIGS. 1, 3˜7, 9 and12 are cross-sectional schematic drawings of a pressure-reducing chambertaken along the vertical direction of a container. As shown in FIG. 1,the manufacturing apparatus has a container side electrode 3 which formsone portion of a pressure-reducing chamber 6 which houses a container 7formed from plastic in which the cross-sectional area of an opening 10of the container 7 is made smaller than the cross-sectional area of ahorizontal cross section at a body portion of the container 7 andprovided with a neck portion between the opening 10 and the bodyportion, and a facing electrode 5 which faces the container sideelectrode 3 and is arranged inside the container 7 or above the opening10, wherein the container side electrode 3 and the facing electrode 5are made to face each other via an insulating body 4 which forms aportion of the pressure-reducing chamber 6, source gas supply means 18which supply a source gas that is converted to plasma for coating theinner wall surface of the container 7 with a DLC film includes a supplygas inlet pipe 9 provided in the pressure-reducing chamber 6 tointroduce the source gas supplied to the pressure-reducing chamber 6 tothe inside of the container 7, exhaust means 21 which exhaust gas insidethe pressure-reducing chamber 6 from above the opening 10 of thecontainer 7 are provided, and high frequency supply means 14 whichsupply a high frequency is connected to the container side electrode 3.

The container side electrode 3 is constructed from an upper electrode 1and a lower electrode 2 which can be attached to and removed from theupper electrode 1. An O-ring 8 is arranged between the upper electrode 1and the lower electrode 2 to ensure airtightness. The upper electrode 1and the lower electrode 2 form a conducting state so as to form one bodyas a container side electrode. The container side electrode 3 has astructure that is divided into the upper electrode 1 and the lowerelectrode 2 to provide a housing opening for housing the plasticcontainer 7 inside the container side electrode 3. In FIG. 1, thecontainer side electrode 3 is divided to form the two upper and lowerportions, but it may be divided to form three upper, middle and lowerportions for housing the container, or it may be divided vertically.

The container side electrode 3 shown in FIG. 1 is given a shape whichhouses the container 7 excluding the mouth portion of the container 7.The reason for this is that it reduces the formation of a DLC film onthe inner wall surface of the mouth portion. Accordingly, in the casewhere a DLC film is formed on the inner wall surface of the mouthportion, a shape may be formed to house the entire container. Further,in order to adjust the film forming region, a shape may be formed tohouse the container excluding the mouth portion of the container and oneportion of the neck portion.

Further, as shown in FIG. 2, the container side electrode 3 is formed sothat the average inner hole diameter (R2) of the inner wall surroundingthe container neck portion when the container is housed becomes smallerthan the average inner hole diameter (R1) of the inner wall surroundingthe body portion. At the same time, the container side electrode 3 isformed so that the average distance (d2; defined as the average neckportion offset length) between the container outer wall and the innerwall of the container side electrode in a horizontal cross section withrespect to the vertical direction of the container at the neck portionbecomes smaller than the average distance (d1; defined as the averagebody portion offset length) between the container outer wall and theinner wall of the container side electrode in a horizontal cross sectionwith respect to the vertical direction of the container at the bodyportion. Further, d1 is preferably made sufficiently small so that theself bias produced at the container body portion wall surface at thetime of plasma generation is not lowered more than necessary, and toavoid plasma concentration at the neck portion. Even though d1 willchange depending on the container capacity and the film formingconditions, it is preferably greater than 0 mm and less than or equal to4 mm. The relationship R2<R1 is established because in the relationshipR2≧R1, the neck portion offset length is too long, and it is notpossible to secure a required oxygen barrier property as describedlater. Further, when there is the relationship R2=R1, the inner wall ofthe container side electrode 3 forms a cylindrical shape. On the otherhand, the relationship d2>d1 is established to suppress increase of theplasma density at the neck portion by providing a moderate neck portionoffset, and to mitigate plasma damage or a plasma etching effect to theDLC film. Further, the relationship d2=d1 is the case where the outerwall of the container and the inner wall of the space of the containerside electrode have similar shapes which almost touch.

When (R2<R1) and (d2>d1) are satisfied, the average neck portion offsetlength d2 preferably forms a distance that suppresses the increase ofplasma density accompanying the increase in pressure of the source gasconverted to plasma at the neck portion inside the container in order toform a roughly uniform plasma density inside the container. By makingthe plasma density uniform, degradation due to plasma damage or plasmaetching of the DLC film formed on the neck portion is mitigated.

When (R2<R1) and (d2>d1) are satisfied, the average neck portion offsetlength d2 is formed to be the same as or shorter than the distance atwhich the strength of ionic impacts due to collisions of the ions of thesource gas converted to plasma with the inner wall surface of thecontainer forms an ionic impact strength capable of forming a DLC filmhaving a prescribed lower limit oxygen barrier property. At the sametime as this, the average neck portion offset length d2 is preferablyformed to be the same as or shorter than the distance at which theentire wall surface of the container has a roughly uniform color bysuppressing coloration of a specific part of the container from the neckportion to the opening caused by plasma damage or plasma etching of theinner wall surface of the container due to the increase in plasmadensity accompanying the increase in pressure of the source gasconverted to plasma in the neck portion inside the container.

In the apparatus of the present invention, the formation of a DLC filmon the inner wall surface of the container 7 is carried out by a plasmaCVD method. Namely, discharging is produced by the high frequencyapplied between the container side electrode 3 and the facing electrode5, plasma is generated, and if the conditions for continuing dischargeare satisfied, the plasma discharge is stabilized. Then, the source gasis decomposed by the plasma to form various kinds of radicals (most ofwhich are ionized to positive). On the other hand, the electronsproduced by discharging accumulate on the inner wall surface, and aprescribed potential drop (the application of a self bias voltage) iscreated, whereby a potential well (called a sheath potential) ispossible. Then, the energy of the kinds of radicals ionized at the innerwall surface of the container 7 are accelerated by the sheath potentialcreated on the container wall surface, and these randomly collide withthe entire inner surface of the inner wall surface. At this time, theundecomposed radicals and ions are finally decomposed on the inner wallsurface of the container, and if the source gas is a hydrocarbon gas,there is bonding between adjacent carbon atoms and between carbon atomsand hydrogen atoms, and the release of temporarily bonded hydrogen atoms(a spattering effect) occurs. When the above processes are carried out,a very fine DLC film is formed on the inner wall surface of thecontainer 7. By applying a moderate high frequency output and selectinga suitable gas flow rate, plasma discharge will continue between thecontainer side electrode 3 and the facing electrode 5.

In this regard, if the strength of ionic impacts due to collisions ofthe ions of the source gas converted to plasma with the inner wallsurface of the container is weak, a fine DLC film will not be obtained,and an oxygen barrier property will not be obtained. As the average neckportion offset length d2 becomes larger, the self bias voltage becomessmaller and the strength of the ionic impacts becomes weaker.Accordingly, the average neck portion offset length d2 must be anaverage neck portion offset length d2 that obtains an ionic impactstrength greater than or equal to an ionic impact strength capable offorming a DLC film having a prescribed lower limit oxygen barrierproperty. Namely, the average neck portion offset length d2 needs to beformed to be the same as or shorter than the distance at which thestrength of ionic impacts due to collisions of the ions of the sourcegas converted to plasma with the inner wall surface of the containerforms an ionic impact strength capable of forming a DLC film having aprescribed lower limit oxygen barrier property. In this regard, theprescribed lower limit oxygen barrier property is an oxygen permeabilityof 0.0050 ml/container (500 ml PET container)/day (23° C. and RH90%,measurement values after 20 hours from the start of nitrogen gasreplacement).

When the average neck portion offset length d2 becomes shorter, the selfbias voltage becomes higher. Then, with regard to the shoulder portionin comparison with the body portion, because an increase in plasmadensity occurs accompanying the increase in pressure of the source gasconverted to plasma at the neck portion inside the container, there ismore exposure to excessive plasma than there is at the body portion,whereby coloration at a specific part of the container from the neckportion to the opening is created by degradation (bonding state and thelike) due to plasma damage or plasma etching. In order to make theentire wall surface of the container have a roughly uniform color, theaverage neck portion offset length d2 needs to be made sufficiently longso that this coloration does not occur.

To summarize the above, the average neck portion offset length d2 ispreferably formed to be a distance at which the DLC film coated plasticcontainer secures a prescribed oxygen barrier property and the entirewall surface of the DLC film coated plastic container has a roughlyuniform color. Further, the prescribed oxygen barrier property is anoxygen permeability which is less than or equal to 0.0050 ml/container(500 ml PET container)/day (23° C. and RH90%, measurement values after20 hours from the start of nitrogen gas replacement).

Further, the average neck portion offset length d2 is calculated fromEquation 1. As indicated by the symbols in FIG. 2, the average diameterof the body portion of the container is made D1, the average diameter ofthe neck portion is made D2, and in the case where K is made the offsetcoefficient that satisfies the relationship of Equation 1, the offsetcoefficient K satisfies the relationship of Equation 2 or Equation 3.

d2=K×(D1−D2)/2+d1  (Equation 1)

0.29≦K≦0.79 where 0.2 mm≦d1≦2.0 mm  (Equation 2)

0.11≦K≦0.51 where 2.0 mm<d1≦4.0 mm  (Equation 3)

In this regard, the average diameter of the body portion is the diameterof a cylinder in the case where the container body portion isapproximated by a cylindrical shape having the same height and the samevolume. The average diameter of the neck portion is the diameter of acylinder in the case where the container neck portion is approximated bya cylindrical shape having the same height and the same volume.

In this regard, the offset coefficient K is a parameter used at the timethe average neck portion offset length d2 is determined using D1, D2 andd1, and when K=0, this forms d2=d1, and the inner wall of the spacehousing the container of the container side electrode 3 forms a similarshape that almost touches the container. On the other hand, when K=1,this forms d2=(D1−D2)/2+d1, and the inner wall of the space housing thecontainer of the container side electrode 3 forms a cylindrical shape.The average neck portion offset length d2 at the time of forming adistance at which the DLC film coated plastic container secures aprescribed oxygen barrier property and the entire wall surface of theDLC film coated plastic container has a roughly uniform color isdetermined by the offset coefficient K given by Equation 2 or Equation3.

Further, in order to compensate the container shape dependency ofEquation 1, the average neck portion offset length d2 may be determinedfrom Equation 4 by introducing the container compensation coefficient αshown in Equation 5. At this time, the offset coefficient K satisfiesthe relationship of Equation 2 or Equation 3.

d2=αK×(D1−D2)/2+d1  (Equation 4)

α=(D1/D2)²/3.54  (Equation 5)

In the case where the container has an axial symmetrical shape withrespect to the central axis of the vertical direction, the inner wallshape of the container side electrode 3 is preferably formed to be anaxial symmetrical shape with respect to the container central axis whenthe container is housed. In this case, because a horizontal crosssection of the container with respect to the central axis forms acircular shape, the inner wall of the container side electrode 3 alsoforms a circular shape concentric with this. In this way, the offsetlength on a horizontal cross section of the container with respect tothe central axis becomes the same everywhere. Accordingly, it ispossible for the distribution of the self bias voltage created on thecontainer wall surface to be made uniform on a horizontal cross sectionof the container with respect to the central axis.

In the case where the container has an axial symmetrical shape withrespect to the central axis of the vertical direction, when thecontainer is housed in the container side electrode, the inner wall ofthe container side electrode surrounding the body portion of thecontainer may be formed to have a cylindrical shape, the inner wall ofthe container side electrode surrounding the neck portion of thecontainer may be formed to have a truncated cone shaped cylindricalshape in which the diameter becomes smaller toward the containeropening, and the inner wall of the container side electrode may beformed to have a continuous shape that does not have different stages.The present inventors call the container side electrode having thisshape a “cone compound electrode”, and instead of preparing a separatecontainer side electrode to match each of the various shapes of beveragecontainers, for example, this structure provides a container sideelectrode that can be used for all applications. This corresponds to thefact that the mouth portion of the container has a cylindrical shape.

In the cone compound electrode, the shape of the inner wall of the spacecan be constructed from two members comprising a cylindrical baseportion and a cylindrical upper portion having a truncated cone shape.By forming a truncated cone shape, the body portion offset length andthe neck portion offset length can be controlled independently by arelatively simple structure. Further, an optimum electrode structure canbe searched easily for various containers having different shapes.

In the cone compound electrode, the inner wall of the container sideelectrode surrounding the opening of the container may be formed to havea cylindrical shape.

On the other hand, in the case of so-called square bottles where thebody portion of the container has a square tube shape, the inner wall ofthe container side electrode surrounding the body portion of thecontainer may be formed to have a square tube shape, the inner wall ofthe container side electrode surrounding the neck portion of thecontainer may be formed to have a truncated pyramid shaped square tubeshape in which the diameter becomes smaller toward the containeropening, a square tube shape or a shape which is a combination of these,and the inner wall of the container side electrode (hereafter referredto as a “pyramid compound electrode”) may be formed to have a continuousshape that does not have different stages. A DLC film coating can beobtained even when a film is formed on a square tube shaped containerusing the cone compound electrode described above, but the pyramidcompound electrode is preferably applied in order to apply a uniformself bias voltage to the wall surface of the square bottle.

In the pyramid compound electrode, the shape of the inner wall of thespace can be constructed from two members comprising a square tube baseportion and a square tube upper portion having a truncated pyramidshape, and the body portion offset length and the neck portion offsetlength can be controlled independently by a relatively simple structure.Further, an optimum electrode structure can be searched easily forvarious containers having different shapes.

In the pyramid compound electrode, the inner wall of the container sideelectrode surrounding the opening of the container may be formed to havea square tube shape. This corresponds to the fact that the mouth portionof the container has a cylindrical shape. Further, the inner wall of thecontainer side electrode surrounding the opening of the container may beformed to have a cylindrical shape, but in this case, stages will becreated in the inner wall of the space of the container side electrodehousing the container.

In the case where a pyramid compound electrode is used, in particular inthe case of a 90° rotation object container, by substituting the lengthof one side in a horizontal cross section with respect to the containercentral axis at the body portion for D1 of Equation 4 and Equation 5,and by substituting the average length of one side in a horizontal crosssection with respect to the container central axis at the neck portionfor D2 of Equation 4 and Equation 5, K satisfies Equation 2 and Equation3, and based on that, d2 can be calculated from Equation 4.

Next, a description will be given for the facing electrode 5. The facingelectrode 5 is an electrode that faces the container side electrode 3.Accordingly, because the facing electrode 5 and the container sideelectrode 3 need to form an insulating state, the insulating body 4 isprovided between these electrodes. The facing electrode 5 is arranged soas to be positioned above the opening 10 of the container. At this time,the entire facing electrode 5 or a portion thereof is preferablyarranged near the opening 10 of the container. This shortens thedistance to the container side electrode 3, and makes the plasmadistribution become a uniform distribution inside the container.Further, the shape of the facing electrode 5 can be freely formed, butas shown in FIG. 1, the facing electrode is preferably equipped with anannular portion 11 having roughly the same inner hole diameter as theopening diameter of the plastic container 7. This facing electrode isformed so that the opening of the end of the annular portion 11 isaligned on the same axis for the opening 10 of the plastic container 7and arranged near the opening 10 of the plastic container 7. The reasonfor forming an annular shape is because this makes it possible toprevent an increase of the exhaust resistance caused by the facingelectrode. Further, the facing electrode 5 is preferably grounded.

In the present invention, as shown in FIG. 3, the facing electrode 5 isformed to have a tubular portion 5 a which hangs down from the topportion of the pressure-reducing chamber to a position above the opening10 of the plastic container 7, the source gas supplied by the source gassupply means 18 is introduced to the inside of the tubular portion 5 a,and the end 5 b of the tubular portion 5 a may be connected to thesource gas inlet pipe 9. At this time, the end 5 b of the tubularportion 5 a is preferably arranged near the opening 10 of the plasticcontainer 7. In the case of FIG. 3, the end 5 b forms splicing means forconnecting the tubular portion and the source gas inlet pipe. By formingthis kind of structure, it is possible to eliminate the lowering ofexhaust conductance as the facing electrode is brought near the opening10. Accordingly, the plasma discharge is easily stabilized.

The facing electrode or the end of the annular portion 11 of FIG. 1 orthe end of the tubular portion of FIG. 3 preferably makes contact withthe gas flow formed from a position near the opening 10 of the plasticcontainer 7 to an exhaust port 23 of the pressure-reducing chamber 6 bythe exhaust means 21. This makes it possible to easily generate plasmaand stabilize the discharge.

Further, by providing the facing electrode with the annular portion 11of FIG. 1 or the tubular portion of FIG. 3, it is possible to reduce theunevenness of plasma distribution inside the plastic container in thecircumferential direction of the container side, and this makes itpossible to reduce the unevenness of the film distribution.

In the manufacturing apparatus of the present invention, in addition tothe apparatus shown in FIG. 1 or FIG. 3, a facing electrode 5 c may beformed to have a shape that is arranged inside the plastic container 7,namely, the facing electrode 5 c may be formed as an internal electrodehaving an electrode shape that is inserted inside the container. At thistime, the source gas inlet pipe is also used as the facing electrode 5 cwhich is a conducting body.

Further, the material of the container side electrode and the facingelectrode is preferably stainless steel (SUS) or aluminum.

The insulating body 4 serves the role of forming an insulating statebetween the facing electrode 5 and the container side electrode 3, andalso serves the role of forming one portion of the pressure-reducingchamber 6. The insulating body is formed by a fluororesin, for example.The pressure-reducing chamber 6 is formed by assembling the containerside electrode 3, the insulating body 4 and the facing electrode 5 to bemutually airtight. Namely, an O-ring is arranged between the containerside electrode 3 and the insulating body 4 to ensure airtightness.Further, an O-ring (not shown in the drawings) is also arranged betweenthe insulating body 4 and the facing electrode 5 to ensure airtightness.In the apparatus of FIG. 1, a structure is formed in which the facingelectrode 5 is provided above the insulating body 4, but when the facingelectrode 5 forms a facing electrode that faces the container sideelectrode 3, because the size thereof can be freely set, the size of themember formed from the insulating body 4 and the facing electrode 5shown in FIG. 1 may be fixed, and the insulating body may be formedlarge with the facing electrode being made smaller by just that sizeportion. Alternatively, the insulating body may be formed small enoughto serve the role of only a rough insulator with the facing electrodebeing made larger by just that size portion. A space 40 is formed insidethe member formed from the insulating body 4 and the facing electrode 5,and the space 40 together with the space inside the plastic container 7form a pressure-reducing space. The pressure-reducing chamber 6 formsthis pressure-reducing space.

The source gas inlet pipe 9 is formed to have a hollow (cylindrical)shape. The material in the case where the apparatus is constructed sothat the facing electrode is arranged outside the container as in FIG. 1or FIG. 3 is preferably formed from a resin material having aninsulating property and heat resistance sufficient to endure plasma. Inthis regard, fluororesin, polyamide, polyimide, and polyether etherketone can be used as examples of a resin material. Alternatively, thesource gas inlet pipe 9 is preferably formed from a ceramic materialhaving an insulating property. Alumina, zirconia, titania, silica andquartz glass can be used as examples of a ceramic material. Further, inthe case where the apparatus is constructed so that the facing electrode5 c is inserted inside the container as in FIG. 4, the source gas inletpipe 9 is formed by stainless steel or aluminum. The source gas inletpipe 9 is provided inside the pressure-reducing chamber 6 so as to bearranged inside the plastic container 7 by being freely inserted andremoved through the opening 10 of the container. At this time, thesource gas inlet pipe 9 is supported on the pressure-reducing chamber 6.As for the method of support, the source gas inlet pipe 9 can besupported on the facing electrode 5 as shown in FIG. 1, for example, orthe source gas inlet pipe 9 can be supported on the tubular portion 5 avia the splicing means as shown in FIG. 3. Further, one blowout hole (9a) which communicates the inside and the outside of the source gas inletpipe 9 is formed on the lower end of the source gas inlet pipe 9.Further, instead of providing a blowout hole at the lower end, aplurality of blowout holes (not shown in the drawings) may be formed topass through the inside and the outside of the source gas inlet pipe 9in radial directions. The source gas inlet pipe 9 is connected to theend of a pipeline of the source gas supply means 18 which communicateswith the inside of the source gas inlet pipe 9. Further, the apparatusis constructed so that the source gas sent into the inside of the sourcegas inlet pipe 9 via the pipeline can be blown into the inside of theplastic container 7 via the blowout hole 9 a. Further, by forming thesource gas inlet pipe 9 by an insulating material, it is possible toreduce the adherence of source gas type dust to the external surface ofthe source gas inlet pipe 9.

By inserting the tip portion of the source gas inlet pipe 9 through theopening of the plastic container to a position near the mouth portion asshown in FIG. 5 or FIG. 6, it becomes possible to supply source gas tothe entire inside of the plastic container. In this regard, the tip ofthe source gas inlet pipe shown in FIG. 1, FIG. 3 or FIG. 4 is morepreferably arranged to be freely inserted to and removed from a deepposition reaching the bottom portion from the body portion through theopening of the plastic container. The reason for this is that it makesit possible to form a turbulence-free source gas flow from the bottomportion of the container to the opening as shown in FIG. 7, and thismakes it possible to form a DLC film more uniformly on the inner wallsurface of the container.

Further, in the apparatus of the present invention, the source gas inletpipe is inserted inside the plastic container at the time a source gasis introduced, and source gas inlet pipe insertion/removal means (notshown in the drawings) may be provided to place the source gas inletpipe in a removed state from the plastic container at the time plasma isgenerated. The source gas inlet pipe insertion/removal means make itpossible to distribute source gas and form a DLC film over the entireinside of the plastic container, and there is absolutely no adherence ofdust because the source gas inlet pipe make it possible to remove thesource gas inlet pipe from the plasma region at the time a film isformed. Further, in the case where source gas inlet pipeinsertion/removal means are provided to place the source gas inlet pipein a removed state from the plastic container when plasma is generated,a valve (shutter) (not shown in the drawings) which can be freely openedand closed for the purpose of controlling the exhaust rate of the sourcegas is preferably provided near the opening 10.

Further, dust incineration means (not shown in the drawings) may beprovided to incinerate dust adhering to a ceramic material type sourcegas inlet pipe 9 in the present apparatus. Two or more source gas inletpipes which can be arranged in an alternating manner are prepared, andafter a film is formed a prescribed number of times, the arrangement ofthe source gas inlet pipes are switched, and the dust adhering to thesource gas inlet pipe in standby is incinerated by operating the dustincineration means.

The source gas supply means 18 introduces the source gas supplied from asource gas generating source 17 to the inside of the plastic container7. Namely, one side of a pipeline 16 is connected to the facingelectrode 5 or the insulating body 4, and the other side of the pipeline16 is connected to one side of a mass flow controller (not shown in thedrawings) via a vacuum valve (not shown in the drawings). The other sideof the mass flow controller is connected to the source gas generatingsource 17 via a pipeline. The source gas generating source 17 generatesa hydrocarbon gas or the like such as acetylene or the like.

Aliphatic hydrocarbons, aromatic hydrocarbons, oxygen-containinghydrocarbons, nitrogen-containing hydrocarbons and the like which form agas or liquid at room temperature are used as a source gas. Inparticular, benzene, toluene, o-xylene, m-xylene, p-xylene, cyclohexaneand the like having a carbon number of 6 or higher are preferred.Ethylene type hydrocarbons and acetylene type hydrocarbons representexamples of aliphatic hydrocarbons. These materials may be usedseparately or as a gas mixture or two or more types. Further, thesegases may be used in a way in which they are diluted by a noble gas suchas argon or helium. Further, in the case where a silicon-containing DLCfilm is formed, a Si-containing hydrocarbon type gas is used.

The DLC film in the present invention refers to an amorphous carbon filmcontaining sp³ bonding which is a carbon film that is also called ani-carbon film or a hydrogenated amorphous carbon film (a-CH). The amountof hydrogen contained in the DLC film which sets the film quality fromhardness to softness (polymer like) is in the range from 0 atom % to 70atom %.

The exhaust means 21 is constructed from a vacuum valve 19 and anexhaust pump 20 as well as a pipeline that connects these. The space 40formed inside the member formed from the insulating body 4 and thefacing electrode 5 is connected to one side of an exhaust pipeline. Forexample, in FIG. 1, an exhaust pipeline is connected to the exhaust port23 provided in the facing electrode 5. The other side of the exhaustpipeline is connected to the exhaust pump 20 via the vacuum valve 19.The exhaust pump 20 is connected to an exhaust duct (not shown in thedrawings). By operating the exhaust means 21, pressure is reduced in apressure-reducing space formed from the space 40 and the space insidethe container inside the pressure-reducing chamber 6.

The high frequency supply means 14 is formed from a matching box 12which is connected to the container side electrode 3, and a highfrequency power source 13 which supplies a high frequency to thematching box 12. The matching box 12 is connected to the output side ofthe high frequency power source 13. In FIG. 1, the high frequency supplymeans 14 is connected to the lower electrode 2, but it may also beconnected to the upper electrode 1. Further, the high frequency powersource 13 is grounded. The high frequency power source 13 generates ahigh frequency voltage between itself and the ground potential, and inthis way a high frequency voltage is applied between the container sideelectrode 3 and the facing electrode 5. In this way, the source gasinside the plastic container 7 is converted to plasma. The frequency ofthe high frequency power source is 100 kHz˜1,000 MHz, and the industrialfrequency of 13.56 MHz is used, for example.

The container according to the present invention includes a containerthat uses a cover or a stopper or is sealed, or a container used in anopen state that does not use these. The size of the opening isdetermined in accordance with the contents. The container shape isespecially preferred to be a container shape having a neck portion inwhich the cross-sectional area of the opening of the container is madesmaller than the cross-sectional area of a horizontal cross section atthe body portion of the container. This is because in a container havingthis shape, the pressure increases at the neck portion when the sourcegas flows, and this also increases the plasma density, whereby the DLCfilm receives plasma damage or plasma etching. Further, the plasticcontainer includes a plastic container having a moderate stiffness and aprescribed thickness, and a plastic container formed from a sheetmaterial that does not have stiffness. The substance that is filled intothe plastic container according to the present invention can be abeverage such as a carbonated beverage or a fruit juice beverage or asoft drink or the like, as well as a medicine, an agricultural chemical,or a dried food which hates moisture absorption. Further, the containermay be either a returnable container or a one-way container.

Further, in the present invention, each part of a beverage container ora container having a shape similar to this is named as shown in FIG. 8.

The resin used when forming the plastic container 7 of the presentinvention can be polyethylene terephthalate (PET) resin, polybutyleneterephthalate resin, polyethylene naphthalate resin, polyethylene resin,polypropylene (PP) resin, cycloolefin copolymer (COC, annular olefincopolymer) resin, ionomer resin, poly-4-methylpentene-1 resin,polymethyl methacrylate resin, polystyrene resin, ethylene-vinyl alcoholcopolymer resin, acrylonitrile resin, polyvinyl chloride resin,polyvinylidene chloride resin, polyamide resin, polyamide-imide resin,polyacetal resin, polycarbonate resin, polysulfone resin, or ethylenetetrafluoride, acrylonitrile-styrene resin,acrylonitrile-butadiene-styrene resin, for example. Of these, PET isparticularly preferred.

In the present invention, in a manufacturing apparatus in which thefacing electrode 11 or 5 a is arranged above the container openingtaking FIG. 1 or FIG. 3 as an example, or in a manufacturing apparatusin which a so-called internal electrode is arranged by arranging thefacing electrode 5 c inside the container taking FIG. 4 as an example,exhaust conductance adjustment means 50 are preferably provided to carryout adjustment by restricting the amount of gas exhaust that isexhausted from a horizontal cross section of the pressure-reducingchamber 6 above the opening 10 of the plastic container 7 as shown inFIG. 9, for example.

In order to describe the exhaust conductance adjustment means 50 indetail, a description will be given using FIG. 10. FIG. 10( a) is aschematic drawing showing one embodiment of the exhaust conductanceadjustment means 50 in a cross section taken in the plane formed by theaxial direction of the source gas inlet pipe 9 and the insertiondirection of a restrictor 51 of the exhaust conductance adjustment means50. FIG. 10( b) is a cross-sectional schematic drawing taken along X-Xin FIG. 9, and is the case where the restrictor 51 is open. FIG. 10( c)is a cross-sectional schematic drawing taken along X-X in FIG. 9, and isthe case where the restrictor 51 is closed. Further, the object shown bythe symbol 52 in FIG. 10 is a horizontal cross section of thepressure-reducing space inside the pressure-reducing chamber above thecontainer opening, and is a through hole of the pressure-reducingchamber that allows exhaust gas to flow. At this time, in order toadjust the flow of gas exhausted from the container, the exhaustconductance adjustment means 50 is provided above the container opening.

The exhaust conductance adjustment means 50 (a special gate valve) isformed from the restrictor 51 and a restrictor opening/closing mechanism53 which opens and closes the restrictor 51. The restrictor 51 isinstantly moved toward the source gas inlet pipe by the restrictoropening/closing mechanism 53 to cover the through hole 52 of thepressure-reducing chamber. FIG. 10( c) shows the case where therestrictor 51 is moved completely to the end. In this way, it becomespossible to adjust the amount of exhaust gas exhausted from thecontainer. Further, in the exhaust conductance adjustment means 50 shownin FIG. 10, an insertion guide 53 for the source gas inlet pipe 9 is cutinto the restrictor 51, and due to the existence of the insertion guide53, the through hole 52 of the pressure-reducing chamber is notcompletely covered even when the restrictor 51 is restricted as in FIG.10( c). Accordingly, the exhaust conductance adjustment means 50 shownin FIG. 10 does not completely shut off the flow of gas exhausted fromthe container.

Instead of the embodiment shown in FIG. 10, the exhaust conductanceadjustment means 50 may be constructed to open and close the throughhole 52 by moving two restrictors having the same shape as therestrictor 51 of FIG. 10 toward each other in a symmetrical arrangementwith respect to the source gas inlet pipe. When this structure isformed, because the insertion guide described above is mutually coveredby the two restrictors, it becomes possible to almost completely shutoff the flow of gas exhausted from the container.

Further, the shut off degree of the flow of gas exhausted from thecontainer may be adjusted by a restricting mechanism that is the same asa light quantity restricting mechanism of a camera in which the sourcegas inlet pipe forms a centripetal axis for the purpose of opening andclosing the through hole 52 of the pressure-reducing chamber.

The above-mentioned three embodiments of the exhaust conductanceadjustment means 50 were described, but other embodiments of arestrictor may be formed for the purpose of opening and closing thethrough hole 52 of the pressure-reducing chamber.

It becomes possible to adjust the flow of gas exhausted from thecontainer over a wide range by operating the separate opening andclosing of the exhaust conductance adjustment means 50, or operating theopening and closing of the vacuum valve 19, or operating the opening andclosing of the exhaust conductance adjustment means 50 and the vacuumvalve 19 by the exhaust conductance adjustment means 50 provided abovethe container opening.

In the present embodiment, an apparatus of the type in which the openingof the container faces upward is shown, but it is also possible to forma pressure-reducing chamber in which the top and bottom are reversed.

Further, in the present embodiment, a DLC film is the thin film formedby the manufacturing apparatus, but it is also possible to use the filmforming apparatus described above when forming a Si-containing DLC filmor other thin film.

Next, with reference to FIG. 1, a description will be given for aprocess in the case where a DLC film is formed on the inner wall surfaceof the plastic container 7 using the present apparatus.

(Manufacturing Method 1)

(Loading Container in Manufacturing Apparatus)

First, a vent (not shown in the drawings) is opened, and the inside ofthe pressure-reducing chamber 6 is opened to the atmosphere. In thisway, air enters the space 40 and the space inside the plastic container7, and the inside of the pressure-reducing chamber 6 reaches atmosphericpressure. Next, the lower electrode 2 of the container side electrode 3is removed from the upper electrode 1, and the plastic container 7 isset so that the bottom portion thereof makes contact with the topsurface of the lower electrode 2. A PET bottle is used as the plasticcontainer 7, for example. Then, by raising the lower electrode 2, theplastic container 7 is housed in the pressure-reducing chamber 6. Atthis time, the source gas inlet pipe 9 provided in the pressure-reducingchamber 6 is passed through the opening 10 of the plastic container 7and inserted inside the plastic container 7, and the facing electrode 5is arranged above the opening of the container. Further, the containerside electrode 3 is sealed by the O-ring 8.

(Operation to Reduce Pressure in Pressure-Reducing Chamber)

When the lower electrode 2 is raised to a prescribed position and thepressure-reducing chamber 6 is sealed, a state is formed in which theperiphery of the plastic container 7 makes contact with the innersurface of the lower electrode 2 and the upper electrode 1. Next, afterclosing the vent, the exhaust means 21 is operated to exhaust the airinside the pressure-reducing chamber 6 through the exhaust port 23.Then, the pressure inside the pressure-reducing chamber 6 is reduceduntil a required vacuum level of 4 Pa, for example, is reached. This isbecause there will be too many impurities inside the container when thevacuum level is allowed to exceed 4 Pa.

(Introduction of Source Gas)

Then, the source gas (e.g., a carbon source gas such as an aliphatichydrocarbon, an aromatic hydrocarbon or the like) sent from the sourcegas supply means 18 which controls the flow rate is introduced insidethe plastic container 7 from the blowout hole 9 a of the source gasinlet pipe 9. The source gas supply rate is preferably 20˜50 ml/min. Theconcentration of the source gas becomes fixed, and a prescribed filmforming pressure is stabilized at 7˜22 Pa, for example, by balancing thecontrolled gas flow rate and the exhaust capacity.

(Plasma Film Formation)

By operating the high frequency power source 13, a high frequencyvoltage is applied between the facing electrode 5 and the container sideelectrode 3 via the matching unit 12, and source gas type plasma isgenerated inside the plastic container 7. At this time, the matchingunit 12 matches the impedance of the container side electrode 3 and thefacing electrode 5 by the inductance L and the capacitance C. In thisway, a DLC film is formed on the inner wall surface of the plasticcontainer 7. Further, the output (e.g., 13.56 MHz) of the high frequencypower source 13 is approximately 200˜500 W.

Namely, the formation of a DLC film on the inner wall surface of theplastic container 7 is carried out by a plasma CVD method. Namely, asdescribed above, a self bias voltage is applied to the container wallsurface, and the ions of the source gas converted to plasma areaccelerated in accordance with the strength of the self bias voltage andspattered on the container inner wall surface, whereby a DLC film isformed. By carrying out a CVD process, a very fine DLC film is formed onthe inner wall surface of the plastic container 7. By applying amoderate high frequency output, plasma discharge is continued betweenthe container side electrode 3 and the facing electrode 5. The filmformation time is several seconds which is short.

At this time, by providing a neck portion offset like that in theapparatus of FIG. 1 or FIG. 3, the self bias voltage of the neck portionis lowered moderately, and degradation of the film quality of the DLCfilm due to plasma damage or plasma etching caused by a concentration ofplasma density at the neck portion is mitigated.

Further, after the concentration of source gas becomes fixed andstabilization at a prescribed film formation pressure is achieved bybalancing the controlled gas flow rate and the exhaust capacity, thesource gas inlet pipe may be removed from the plastic container beforeplasma generation by operating the source gas inlet pipeinsertion/removal means, and then source gas type plasma may begenerated inside the plastic container 7 by applying a high frequencyvoltage between the facing electrode 5 and the container side electrode3 via the matching unit 12 by operating the high frequency power source13. At this time, because the source gas inlet pipe is not inside theplastic container during plasma discharge, it is possible to almostcompletely suppress the adherence of dust.

(Termination of Film Formation)

The RF output from the high frequency power source 13 is stopped, andthe supply of source gas is stopped. Then, the hydrocarbon gas insidethe pressure-reducing chamber 6 is exhausted by the exhaust pump 20.Then, the vacuum valve 19 is closed, and the exhaust pump 20 is stopped.Then, the vent (not shown in the drawings) is opened to open the insideof the pressure-reducing chamber 6 to the atmosphere, and by repeatingthe above-described film formation method, a DLC film is formed on theinside of the next plastic container. The film thickness of the DLC filmis formed to be 10˜80 nm.

The plastic container manufactured in this way had an oxygenpermeability the same as or lower than the carbon film coated plasticcontainer mentioned in Japanese Laid-Open Patent Application No. HEI8-53117. In the case where a 30 nm (average for the entire container)DLC film was formed on a plastic container having a capacity of 500 ml,a container height of 200 mm, a container body portion diameter of 71.5mm, a mouth portion opening inner diameter of 21.74 mm, a mouth portionopening outer diameter of 24.94 mm, a container body portion thicknessof 0.3 mm, and a resin weight of 32 g/container, the oxygen permeabilitywas 0.0040 ml/container (500 ml PET container)/day (23° C. and RH90%,measurement values after 20 hours from the start of nitrogen gasreplacement).

In the present embodiment, a PET bottle for beverages was used as thecontainer having a thin film formed on the inside, but it is alsopossible to use containers used for other uses.

(Manufacturing Method 2)

With reference to FIG. 9, a description will be given for a filmformation method that roughly fixes the gas pressure inside thecontainer and suppresses the rise of plasma density at the neck portionby adjusting the exhaust of source gas inside the plastic container atthe time of film formation. The special feature of this manufacturingmethod is the structure in which the space of the container sideelectrode has a shape similar to the outer wall of the container,namely, it is a manufacturing method which can eliminate coloration ofthe container neck portion while having an oxygen barrier property evenwhen coating is carried out using an apparatus in which the mouthportion offset length d3, the neck portion offset length d2 and the bodyportion offset length d1 are roughly the same.

The process of loading the container in the manufacturing apparatus isthe same as the process described in Manufacturing Method 1 (loading acontainer in the manufacturing apparatus).

(Operation to Reduce Pressure in Pressure-Reducing Chamber)

The process of reducing the pressure in the pressure-reducing chamber isthe same as the process described in Manufacturing Method 1 (operationto reduce pressure in the pressure-reducing chamber).

(Introduction of Source Gas)

Then, while continuing to exhaust the inside of the pressure-reducingchamber 6, namely, the inside of the plastic container, the source gas(e.g., a carbon source gas such as an aliphatic hydrocarbon, an aromatichydrocarbon or the like) sent from the source gas supply means 18 whichcontrols the flow rate is introduced inside the plastic container 7 fromthe blowout hole 9 a of the source gas inlet pipe 9. At this time, theintroduction rate of the source gas is 20˜50 ml/min, for example. Then,the inside of the plastic container 7 is replaced by the source gas andthe source gas concentration becomes fixed, and a prescribed filmforming pressure is stabilized at 7˜22 Pa, for example, by balancing thecontrolled gas flow rate through the inside of the plastic container 7and the exhaust capacity.

Then, the exhaust of the inside of the plastic container 7 is almostcompletely stopped. The stopping of the exhaust is carried out byshutting the vacuum valve 19 of FIG. 9 or restricting the restrictor 51of the exhaust conductance means 50 shown in FIG. 9 and FIG. 10 to theclosed position. At the same time the exhaust is stopped, theintroduction rate of the source gas is made smaller than theintroduction rate at the time of replacement by the mass flow controller(not shown in the drawings) of the source gas supply means. At thistime, the introduction rate of the source gas is 5˜20 ml/min, forexample. By carrying out this operation, the flow of source gas insidethe plastic container 7 is slowed, and the pressure distribution insidethe container is made roughly uniform.

(Plasma Film Formation)

After the source gas and the source gas pressure inside the plasticcontainer form the state described above, a DLC film is formed on theinner wall surface of the plastic container 7 by carrying out theoperations described in Manufacturing Method 1 (plasma film formation).Further, the output (e.g., 13.56 MHz) of the high frequency power source13 is approximately 200˜500 W.

The film thickness of the DLC film is formed to be 10˜80 nm.

As described above, after the flow of source gas inside the plasticcontainer 7 is slowed and at the same time the pressure distributioninside the container is made roughly uniform, the flow of source gasinside the container is made smaller by the generation of plasma. Inthis way, there is almost no constriction of source gas accompanying thesudden decrease of cross-sectional area of a horizontal cross section ofthe container vertical axis at the container shoulder portion, thepressure distribution inside the container is uniform, and there is noincrease of plasma density at specific parts. In this way, it ispossible to prevent the DLC film at specific parts from receiving plasmadamage or plasma etching. The DLC film coated plastic container does nothave coloration at the shoulder portion, and is almost transparent witha uniform color.

(Termination of Film Formation)

A process for terminating the film formation is carried out by carryingout the operations described in Manufacturing Method 1 (termination offilm formation).

A plastic container having a capacity of 500 ml, a container height of200 mm, a container body portion diameter of 71.5 mm, a mouth portionopening inner diameter of 21.74 mm, a mouth portion opening outerdiameter of 24.94 mm, a container body portion thickness of 0.3 mm, anda resin weight of 32 g/container was used as the plastic container. Thefilm thickness of the DLC film in this case was 25 nm (average for theentire container).

(Manufacturing Method 3)

With reference to FIG. 9, a description will be given for anotherembodiment of a film formation method that roughly fixes the gaspressure inside the container and suppresses the rise of plasma densityat the neck portion by adjusting the exhaust of source gas inside theplastic container 7 at the time of film formation. The special featureof this manufacturing method is that it is a manufacturing method whichcan eliminate coloration of the container neck portion while having anoxygen barrier property even when coating is carried out using anapparatus in which the space of the container side electrode has a shapesimilar to the outer wall of the container.

The process of loading the container in the manufacturing apparatus isthe same as the process described in Manufacturing Method 1 (loading acontainer in the manufacturing apparatus).

(Operation to Reduce Pressure in Pressure-Reducing Chamber)

The process of reducing the pressure in the pressure-reducing chamber isthe same as the process described in Manufacturing Method 1 (operationto reduce pressure in the pressure-reducing chamber).

(Introduction of Source Gas)

Then, the exhaust rate inside the plastic container 7 is made smaller ormade zero. The adjustment of exhaust is an adjustment of the vacuumvalve 19 of FIG. 9 or an adjustment carried out by restricting therestrictor 51 of the exhaust conductance means 50 shown in FIG. 9 andFIG. 10 to the closed position. Together with this operation, the sourcegas (e.g., a carbon source gas such as an aliphatic hydrocarbon, anaromatic hydrocarbon or the like) sent from the source gas supply means18 which controls the flow rate is introduced inside the plasticcontainer 7 from the blowout hole 9 a of the source gas inlet pipe 9. Atthis time, the introduction rate of the source gas is 5˜40 ml/min, forexample.

(Plasma Film Formation)

Then, at the point in time when the pressure distribution inside theplastic container 7 is roughly uniform and a prescribed pressure isreached, a DLC film is formed on the inner wall surface of the plasticcontainer 7 by carrying out the operations described in ManufacturingMethod 1 (plasma film formation). Further, the output (e.g., 13.56 MHz)of the high frequency power source 13 is approximately 200˜500 W, andthe prescribed pressure inside the container is approximately 10˜50 Pa.

The film thickness of the DLC film is formed to be 10˜80 nm.

In this way, by adjusting the exhaust, after the flow of source gasinside the plastic container 7 is slowed and at the same time thepressure distribution inside the container is made roughly uniform, itis possible to obtain results that are the same as those ofManufacturing Method 2, namely, it is possible to prevent rises inplasma density at specific parts by the generation of plasma. The DLCfilm coated plastic container does not have coloration at the shoulderportion, and is almost transparent with a uniform color.

(Termination of Film Formation)

A process for terminating the film formation is carried out by carryingout the operations described in Manufacturing Method 1 (termination offilm formation).

A plastic container having a capacity of 500 ml, a container height of200 mm, a container body portion diameter of 71.5 mm, a mouth portionopening inner diameter of 21.74 mm, a mouth portion opening outerdiameter of 24.94 mm, a container body portion thickness of 0.3 mm, anda resin weight of 32 g/container was used as the plastic container. Thefilm thickness of the DLC film in this case was 25 nm (average for theentire container).

In Manufacturing Method 2 or Manufacturing Method 3, the manufacturingapparatus of FIG. 9 in which the facing electrode is provided outsidethe container was described as an example, but a manufacturing apparatusin which the internal electrode 5 c is arranged inside the container asa facing electrode like the manufacturing apparatus of FIG. 4 may beused, or a manufacturing apparatus in which exhaust conductance means(the same as the exhaust conductance means 50 of FIG. 9) are provided inthe apparatus of FIG. 4 may be used.

In Manufacturing Method 2 or Manufacturing Method 3, a manufacturingapparatus in which the container side electrode is a similar shapedelectrode like that shown in FIG. 24 may be used. A manufacturingapparatus in which exhaust conductance means (the same as the exhaustconductance means 50 of FIG. 9) are provided in the apparatus of FIG. 24may be used.

Further, in Manufacturing Method 2 or Manufacturing Method 3, theprocesses up to the point before plasma generation are carried out whilethe source gas inlet pipe is in an inserted state in the plasticcontainer, and then after the source gas inlet pipe is removed from theplastic container by operating the source gas inlet pipeinsertion/removal means directly before plasma generation, source gastype plasma may be generated inside the plastic container 7 by applyinga high frequency voltage between the facing electrode 5 and thecontainer side electrode 3 via the matching unit 12 by operating thehigh frequency power source 13. At this time, because the source gasinlet pipe is not inside the plastic container during plasma discharge,it is possible to almost completely suppress the adherence of dust.

Specific Embodiments Examination of Optimum Offset Length

A PET bottle having an axial symmetrical shape with respect to thecentral axis of the vertical direction of the container was used as theplastic container. The plastic container used in the present embodimentsis a PET container having a capacity of 500 ml, a container height of200 mm, a container body portion diameter of 71.5 mm, a mouth portionopening inner diameter of 21.74 mm and outer diameter of 24.94 mm, acontainer body portion thickness of 0.3 mm, and a resin weight of 32g/container of polyethylene terephthalate resin (PET resin RT553manufactured by Nihon Yunipet (Inc.)).

The apparatus used in the present embodiments is the apparatus shown inFIG. 3 or FIG. 4. FIG. 3 shows a manufacturing apparatus in the casewhere a tube made of fluororesin is used as the source gas inlet pipe inan apparatus in which a mouth side electrode 5 a is arranged outside thecontainer. FIG. 4 shows a manufacturing apparatus in the case where SUSis used for the internal electrode 5 c which also functions as a gasinlet pipe. A plurality of cone compound electrode type container sideelectrodes is prepared for examination by changing the standards of theoffset lengths. The offset lengths of the electrodes are shown in Table1 and Table 2. Further, because the electrode is a cone compoundelectrode, the average opening offset length d3, the average neckportion offset length d2 and the average body portion offset length d1are listed respectively as the opening offset length d3, the neckportion offset length d2 and the body portion offset length d1. Becausea container manufactured using the apparatus of either FIG. 3 or FIG. 4will obtain roughly the same results under the same conditions, thecoatings of specific embodiments 1˜16 were carried out by establishingthe conditions of Table 1 and Table 2 in the apparatus of FIG. 3. Thecoatings were carried out in accordance with Manufacturing Method 1.

A DLC film was coated by an apparatus (not shown in the drawings)provided with a cylindrical electrode as Comparative Example 1, and byan apparatus provided with a similar shaped electrode in which thecontainer outer wall and the inner wall of the space of the containerside electrode are almost touching as Comparative Example 2. Thecoatings were carried out in accordance with Manufacturing Method 1. Theconditions of the apparatus are shown in FIG. 3.

TABLE 1 Cone Compound Electrode Type Specific Specific Specific SpecificSpecific Specific Specific Specific Embodiment Embodiment EmbodimentEmbodiment Embodiment Embodiment Embodiment Embodiment Offset 1 2 3 4 56 7 8 Length type 1 type 2 type 3 type 4 type 5 type 6 type 7 type 8Opening 2.0 5.0 8.0 12.0 8.0 2.0 2.0 2.0 offset length (d3)mm Neck 6.28.5 10.5 13.4 10.0 6.4 6.2 6.2 portion offset length (d2)mm Body 3.753.75 3.75 3.75 0.75 0.75 0.75 3.75 portion offset length (d1)mm MaterialAl Al Al Al Al Al Al Al

TABLE 2 Cone Compound Electrode Type Specific Specific Specific SpecificSpecific Specific Specific Specific Embodiment Embodiment EmbodimentEmbodiment Embodiment Embodiment Embodiment Embodiment Offset 9 10 11 1213 14 15 16 Length type 9 type 10 type 12 type 13 type 14 type 15 type16 type 17 Opening 2.0 2.0 2.0 2.0 2.0 5.0 8.0 12.0 offset length (d3)mmNeck 6.2 6.2 7.1 6.8 6.2 8.5 10.5 13.4 portion offset length (d2)mm Body1.75 2.75 2.75 1.75 2.75 2.75 2.75 2.75 portion offset length (d1)mmMaterial Al Al Al Al Al Al Al Al

TABLE 3 Cylindrical Similar Shaped Electrode Electrode ComparativeComparative Offset Length Example 1 Example 2 Opening offset length (d3)2.0 1.5 mm Neck portion offset length 15.8 1.0 (d2)mm Body portionoffset length 1.0 1.0 (d1)mm Material Al Al

Eight standards of the neck portion offset are prepared from 6.2 mm to13.4 mm, and four standards of the body portion offset are prepared. Theelectrodes formed with these standard offset lengths were assembled toform container side electrodes. Further, in the present embodiments, Alis used as the material of the electrodes, but it is clear that the sameelectrode improvement results can be obtained using SUS or anothermetal.

The method of evaluating the DLC film is as follows. The oxygenpermeability of the container was measured under the conditions 23° C.and 90% RH using an Oxtran 2/20 manufactured by Modern Control Company,and measurement values were recorded after 20 hours from the start ofnitrogen gas replacement.

The film thickness of the DLC film was measured using a DEKTAK 3 made byVeeco Company.

The evaluation of the color of the plastic container is indicated by thecoloration degree b* value. The b* value is the color difference of JISK7105-1981, and is calculated by Equation 6 from the tristimulus valuesX, Y and Z.

b*=200[(Y/Y ₀)^(1/3)−(Z/Z ₀)^(1/3)]  (Equation 6)

A U-3500 Model automatic recording spectrophotometer manufactured byHitachi provided with a 600 integrating sphere attached apparatus (forinfrared near visible infrared) manufactured by the same company wasused. An ultrahigh sensitivity photomultiplier (R928: for visibleultraviolet) and a cooling type PbS (for the near infrared region) wereused. As for the measurement wavelengths, the transmittance was measuredin the range from 240 nm to 840 nm. By measuring the transmittance ofthe PET container, it is possible to calculate the transmittancemeasurement of only the DLC film, but the b* value of the presentembodiments as is shows a calculation in a form that includes theabsorptance of the PET container. The correlation with b* in the presentinvention that depends on a visual observation is approximately as shownin Table 4. The b* value of an unprocessed PET container is within therange 0.6˜1.0. Further, when the b* value is 2 or less, the containercan be said to be colorless and transparent. The approximate correlationwith the b* value difference (Δb* value) that depends on the visualobservation is shown in Table 5. In order to satisfy the recyclestandard, it has been determined that b* should be 6 or less, andpreferably 5 or less.

TABLE 4 b* Value 0-2 2-4 4-6 6-8 8- Expression Colorless Very lightLight Slightly Dark by Visual yellowish yellowish yellowish yellowishObservation brown brown brown brown color color color color

TABLE 5 Δb* Value 0-1 1-1.5 1.5-3 3-6 6-12 Expression Almost Very littleSmall Different Very by Visual No difference defference differentObservation difference

In the present embodiments, the film forming conditions of the DLC filmwere set in accordance with Manufacturing Method 1. At this time, exceptwhen specifically stated otherwise, the high frequency power sourceoutput was 400 W, the flow rate of acetylene which was the source gaswas 40 ml/min, and the film forming time was set at 2 seconds. The filmthickness of the DLC film was approximately 30 nm (average for theentire container).

By assembling the 16 types shown in Table 1 and Table 2, a film wasformed under the conditions described above. The body portion offsetlength dependence of the oxygen permeability that depends on thedifference in electrode structure is shown in FIG. 13, the neck portionoffset length dependence of the oxygen permeability that depends on thedifference in electrode structure is shown in FIG. 14, the body portionoffset length dependence of the b* value that depends on the differencein electrode structure is shown in FIG. 15, and the neck portion offsetlength dependence of the b* value that depends on the difference inelectrode structure is shown in FIG. 16.

(Oxygen Barrier Property of Container)

With reference to FIG. 13, under the same film forming conditions, theoxygen permeability becomes higher (the oxygen barrier property becomeslower) as the body portion offset length becomes shorter. This is due toan increase in plasma damage caused by stronger ionic collisions due tothe fact that the plasma density distribution that concentrates at theneck portion increases the plasma damage due to the working of the smalldistribution at the body portion side and makes the sheath potentialbecome large and deep. However, a prescribed oxygen barrier property wassatisfied. The container manufactured by the cylindrical electrode ofComparative Example 1 had a low oxygen barrier property compared withthe containers manufactured by the present invention. With regard to theneck portion offset length dependence, with reference to FIG. 14, underthe same film forming conditions, the oxygen barrier property becomeslower as the body portion offset length becomes shorter. However, forall the body portion offset lengths, the oxygen barrier property of theentire container satisfied a prescribed standard for neck portion offsetlengths up to 13.4 mm. In the case of the cylindrical electrode ofComparative Example 1, the barrier property was low, and the prescribedstandard was not satisfied. Further, from the results of Raman analysis,it was understood that the DLC film of the neck portion of ComparativeExample 1 was a sparse film having few diamond structures, and the DLCfilm of the neck portion of Specific Embodiment 1 was a fine film thatincluded a relatively large number of diamond structures. Accordingly,in order to form a fine DLC film, the neck portion offset length needsto be adjusted to an optimum length to change the self bias and form anoptimum sheath potential. To summarize the above, ranges in which thebody portion offset length is 5.75 mm or less and the neck portionoffset length is 13.4 mm or less are obtained from the oxygenpermeability.

(Coloration of Container)

On the one hand, with regard to the color degree b* value of the film,with reference to the body portion offset length dependence of FIG. 15,except for one portion of data, there is a tendency for the b* value toincrease as the body portion offset length increases. From this fact, atthe least the body portion offset length needs to be 4 mm or less. Thereason for this dependency is that because the effective potentialapplied to the body portion of the container and the facing electrode islowered when the body portion offset length is increased, the plasmadistribution undergoes further movement to the neck portion from thebody portion, and because the plasma distribution becomes moreconcentrated at the neck portion, it is assumed that the conditionsapproach the conditions of the prior art technology, whereby the colorof the film becomes dark. Further, when the data of the neck portionoffset length dependency of FIG. 16 is examined, the color degree b*value becomes larger as the neck portion offset length is reduced in therange where the neck portion offset length is short. This is becauseplasma concentration at the neck portion becomes more remarkable as theelectrode structure approaches Comparative Example 2. On the other hand,when the neck portion offset length at the place where the b* valueshows a minimum value is exceeded, the b* value increases, and beforelong shows a tendency to become saturated. This is assumed to be causedby degradation of the film quality (bonding structure and the like) dueto the lowering of the self bias which makes the ionic collisions at thetime of film formation become smaller when the effective voltage appliedto the container and the facing electrode is reduced accompanying theincrease of the neck portion offset length.

(Examination of Relationship between Oxygen Barrier Property ofContainer and Coloration of Neck Portion)

From the data of the oxygen barrier property and the coloration givenabove, the range of the body portion offset length and the neck portionoffset length forms the range (blackened portion) shown in FIG. 17.Namely, when the body portion offset length is less than or equal to 4mm from the color data, the neck portion offset length changes dependingon the body portion offset length. For example, in the case where thebody portion offset length is 0.2 mm, the neck portion offset length isgreater than or equal to 8.0 mm and less than or equal to 13.4 mm, andin the case where the body portion offset length is 4.0 mm, the neckportion offset length becomes 5.9 mm.

In order to represent this mathematically, an offset coefficient K isintroduced. In the case of the containers of the present embodiments,the correlation between the neck portion offset length and the bodyportion offset length can be prescribed by the equation given below.

d2=K×(D1−D2)/2+d1  (Equation 1)

When K is zero, this represents the cylindrical electrode of ComparativeExample 1, and when K is 1, this represents the similar electrode ofComparative Example 2. By introducing this kind of offset coefficient K,it is possible to obtain the electrode design value of the presentinvention.

The offset coefficient from FIG. 17 and Equation 1 is as follows.

0.29≦K≦0.79 where 0.2 mm≦d1≦2.0 mm  (Equation 2)

0.11≦K≦0.51 where 2.0 mm<d1≦4.0 mm  (Equation 3)

(Introduction of Container Compensation Coefficient α)

The present invention can be applied even in the case of a container inwhich the body portion and the neck portion have different dimensions.With regard to the shape of the container, in order to show that thepresent invention can be applied to other shapes, the constant α isintroduced to give container dependence to Equation 1. In view of thechange in plasma density that depends on the change in size of the neckportion, the degree of plasma concentration at the neck portion isrepresented by the ratio of the body portion average cross-sectionalarea and the neck portion average cross-sectional area of the container.

α=(D1/D2)²/3.54  (Equation 5)

By introducing this equation in Equation 1, the following is obtained.

d2=αK×(D1−D2)/2+d1  (Equation 4)

In the present embodiments, (D1/D2)²=3.54, and because this gives α=1,Equation 4 becomes the same equation as Equation 1.

(Comparison of Prior Art DLC Film Having Large b* Value and DLC FilmHaving Small b* Value Obtained by Apparatus of Present Invention)

The DLC film of the shoulder portion obtained by the manufacturingapparatus of the present invention has a small b* value compared withthe DLC film of the shoulder portion obtained by a prior artmanufacturing apparatus in which the inner wall of the space of thecontainer side electrode housing the container has a similar shape, andthere is clearly a difference even when a comparison is carried out byvisual observation. In order to show this comparison, FIG. 18 shows apicture in which both containers are compared. Further, the case of themanufacturing apparatus of the present invention is mentioned as presentinvention, and the case of the manufacturing apparatus having a similarshaped electrode is mentioned as prior art technology. In the containerof the present invention, the body portion and the neck portion appearto have roughly the same color, there is little irregular color, andsuch color is light. On the other hand, in the container of the priorart technology, the color of the neck portion is darker than the colorof the body portion, and there is irregular color.

It became clear that the light color of the DLC film formed on the neckportion of the present invention is not due a thin film thickness. Thecorrelation of the film thickness and the b* values is shown in FIG. 19.Places having a dark color formed the measurement places. The containerof the present invention was shown to have small b* values regardless ofthe film thickness. In this regard, FIG. 20 shows the opticaltransmittance property at the same portions. The data of the graph isthe optical transmittance property of only the DLC film in which theeffects of the PET base material were eliminated. It was understood thatthe container of the present invention has a slightly higher opticaltransmittance property than the container of Comparative Example 1.Further, in contrast with the container of the present invention whichhas a prescribed oxygen barrier property, the container of ComparativeExample 1 did not achieve the prescribed oxygen barrier property. Fromthe results of Raman analysis, it was understood that the film qualityis degraded (the proportion of diamond bonding is very small).

Further, a comparison of the Raman spectrums of the container of thepresent invention and the container of Comparative Example 2 (prior arttechnology) is shown in FIG. 21, and enlarged views of the DLC relatedportions after the effects due to fluorescence were eliminated are shownin FIG. 22. As for the Raman spectrum, a Super Labram manufactured byJobin Yvon Company was used.

FIG. 21 shows the Raman scattering spectrums (in which the peak of thePET base is subtracted) of Specific Embodiment 1 and Comparative Example2. The writing of DLC in the graph represents a graphite structure peak.Because there is almost no observation of a diamond structure peak byRaman, a form in which evaluation is indirectly carried out from theintensity of the graphite band or the like is formed. From the spectrumof Specific Embodiment 1 of the present invention, it is understood thatComparative Example 2 is the one in which the graphite peak intensity islarge and the graphite mixing proportion or the proportion of carbon(hereafter written as C) double bonds is large. This is assumed to formthe cause of coloration.

FIG. 22 shows enlarged views of the spectrums. As for the graphite band,the G band and the D band are observed, and the D band of the lower wavenumber side is a band that signifies Disorder and reveals the graphitecrystal property will be destroyed. The appearance of the D band isbelieved to correspond to the fact that DLC exists in the film and thegraphite crystal property is being destroyed. In the DLC film, thereexists a mixing of sp² structures and sp³ structures. The D banddescribed above does not appear in the composition region where theproportion of DLC is very small in contrast with the graphite describedabove, and conversely when the proportion of DLC increases, there is atendency for the intensity to be reduced again accompanying the increasein the abundance ratio of sp³ structures (diamond bonding and C—Hbonding) in the DLC film. In the regions of Specific Embodiment 1 andComparative Example 2, the intensity of the D band is weak, but theproportion of sp³ structures is high, and this represents a highproportion of diamond bonding and C—H bonding. In the enlarged views,the graphite bands (G band and D band) appear even in the presentembodiments, but from an intensity comparison of the vertical axis, andfrom the fact that noise is included in the shape of the spectrum andthe fact that both the G band and the D band are weak, it is understoodthat the graphite mixing proportion is low and the ratio of sp³ bondingis high.

Conversely, in Comparative Example 2, it is understood that the peakintensity of the G band is 5.3 times higher compared to the DLC film ofSpecific Embodiment 1, and the graphite mixing proportion is high.

Accordingly, this increase in the proportion of graphite mixing andcarbon double bonds is assumed to make the coloration of the containerneck portion darker.

From the b* value and the results of the Raman spectrums, it becameclear that the DLC film formed on the container neck portion of thepresent invention and the DLC film formed on the container neck portionof the prior art technology are DLC films having different filmqualities (C bonding states and the like). In the apparatus of thepresent invention, there are few graphite type carbon sp² bondingstructures, and because it is possible to form a fine DLC film having ahigh proportion of sp³ bonding structures (diamond structures and thelike) on the container neck portion (and body portion), it is possibleto manufacture a container having a light uniform color over the entirecontainer while securing an oxygen barrier property.

(Examination of Carbon Atom Content, Hydrogen Atom Content and Amount ofGraphite Type Bonding of Film)

The carbon atom content and the hydrogen atom content in the containerneck portion of specific embodiments 1, 2, 3 and 5 and comparativeexamples 1 and 2 are shown in Table 6. In this regard, scaling iscarried out so that the carbon atom content and the hydrogen atomcontent form a total of 100. The measurement device used a RBS(Rutherford backward scattering analyzer) and a HFS (hydrogen forwardscattering measurement apparatus). The accelerator was a 5SDH2manufactured by National Electronics Corporation, the measurement systemwas a RBS400 manufactured by Charls Evans and Associates, and the RBSand the HFS were used together.

TABLE 6 Specific Specific Specific Specific Comparative ComparativeEmbodiment 1 Embodiment 2 Embodiment 3 Embodiment 5 Example 1 Example 2Carbon 37 48 39 43 48 55 Content of Neck portion (atom %) Hydrogen 63 5261 57 52 45 Content of Neck portion (atom %)

The composition proportion of carbon and hydrogen (carbon atom/hydrogenatom) of the DLC film formed on the neck portion was 37/63˜48/52. Inthis regard, there is no difference between the specific embodiments andthe comparative examples with regard to the body portion carbon contentand the body portion hydrogen content, wherein the body portion carboncontent was 55˜75 atom %, and the body portion hydrogen content was25˜45 atom %. Accordingly, in the present embodiments, it is possiblefor the DLC film formed on the neck portion to have higher hydrogen atomcontent than the DLC film formed on the body portion.

Further, in Comparative Example 1, the carbon atom content and thehydrogen atom content in the container neck portion were the same asthose of Comparative Example 2, but the oxygen barrier property was lowas described above, and a prescribed standard was not satisfied.

Next, comparisons of the content of graphite type bonding (SP²) in thecontainer neck portion and the container body portion of specificembodiments 1, 2, 3 and 5 and comparative examples 1 and 2 are shown inTable 7. The comparisons were carried out by conversion to the amount ofgraphite type bonding per each film thickness. The amount of graphitetype bonding was measured using an ESR (electron spin resonanceanalyzing apparatus, JES-FE2XG, manufactured by JEOL).

As is understood from Table 7, the DLC film formed on the neck portionhas a lower graphite mixing proportion than the DLC film formed on thebody portion. Namely, the graphite mixing proportion of the DLC filmformed on the neck portion is 5˜18% of the graphite mixing proportion ofthe body portion.

In Comparative Example 2, the amount of graphite type bond mixing of theneck portion and the body portion are the same level. Accordingly, thereis more coloration of the neck portion as the thickness of the neckportion becomes larger. In the embodiments, because the amount ofgraphite type bond mixing is small, it is possible to prevent colorationeven when the thickness of the neck portion becomes large.

TABLE 7 Specific Specific Specific Specific Comparative ComparativeEmbodiment 1 Embodiment 2 Embodiment 3 Embodiment 5 Example 1 Example 2Amount of 0.38 0.31 0.38 0.12 0.14 1.00 Graphite like bonding of Neckportion Film thickness 62.9 62.7 67.2 64.0 47.4 53.0 of Neck portion(nm) A: Amount of 0.0060 0.0049 0.0057 0.0019 0.0030 0.0019 Graphitelike bonding/film thickness Amount of — — — 0.40 — 0.25 Graphite likebonding of Body portion Film thickness 12.3 10.9 11.6 11.5 11.8 15.0 ofBody portion (nm) B: Amount of — — — 0.0348 — 0.0167 Graphite likebonding/film thickness A/B, where B 17.4 14.2 16.3 5.4 — — is Data ofSpecific Embodiment 5 A/B, where B — — — — 8.5 113.2 is Data ofComparative Example 2

As described above, in the DLC film coated plastic containers of thepresent embodiments, the DLC film formed on the neck portion has a lowerproportion of graphite mixing and a higher hydrogen atom content thanthe DLC film formed on the body portion. Moreover, the oxygenpermeability of the container was ensured to be less than or equal to0.0050 ml/container (500 ml PET container)/day (23° C. and RH90%,measurement values after 20 hours from the start of nitrogen gasreplacement).

(Examination of Container Manufactured by Manufacturing Method 3)

A PET bottle having an axial symmetrical shape with respect to thecentral axis of the vertical direction of the container was used as theplastic container. The plastic container used in the present embodimentsis a PET container having a capacity of 500 ml, a container height of200 mm, a container body portion diameter of 71.5 mm, a mouth portionopening inner diameter of 21.74 mm and outer diameter of 24.94 mm, acontainer body portion thickness of 0.3 mm, and a resin weight of 32g/container of polyethylene terephthalate resin (RT553, PET resinmanufactured by Nihon Yunipet (Inc.)).

The apparatus used by the present embodiments is the apparatus shown inFIG. 24. This is a manufacturing apparatus which uses a similar shapedelectrode. FIG. 24 shows a manufacturing apparatus in the case where SUSis used as an internal electrode which also functions as a gas inletpipe.

Coating was carried out according to the conditions described inManufacturing Method 3. The sequence of Manufacturing Method 3 is shownin FIG. 23. In FIG. 23( a), the air inside the container is sufficientlyexhausted by the vacuum pump in the state where a butterfly valve isopen 100% to secure a vacuum level of 2 Pa. Next, in FIG. 23( b), theopening of the butterfly valve is made 0% or is made smaller, and sourcegas is introduced. The inside of the container is sufficiently filledwith source gas, and the pressure is made uniform at 20˜50 Pa. Next, inFIG. 23( c), a high frequency is applied, the source gas is converted toplasma, and the container inner wall surface is coated with a DLC film.Next (not shown in the drawing), the supply of source gas is stopped,the butterfly valve opening is returned to 100%, the vacuum valve isstopped, and air is introduced inside the container. This formedSpecific Embodiment 17.

In the container of Specific Embodiment 17 manufactured by the processesdescribed above, the average thickness (average for the entirecontainer) of the DLC film was 25 nm, and the b* value of the containerneck portion was 3.8, and this made it possible to manufacture acontainer having a light uniform color over the entire container.Further, the same results were obtained even when the electrode (anelectrode in which the neck portion offset length is larger than thebody portion offset length) of the present invention shown in FIG. 4 wasused.

Further, using the apparatus of FIG. 4, a container was manufacturedaccording to Manufacturing Method 2. This forms Specific Embodiment 18.In the container of Specific Embodiment 18, it was possible to form alight color DLC film on the container neck portion in the same way as inSpecific Embodiment 17. It was possible to manufacture a containerhaving a light uniform color over the entire container while ensuring anoxygen barrier property. Further, the same results were obtained by theapparatus shown in FIG. 24.

A container was manufactured in accordance with Manufacturing Method 3using the manufacturing apparatus in the case where a tube made offluororesin is used as the source gas inlet pipe 9 in the apparatusshown in FIG. 3 in which the mouth side electrode 5 is arranged outsidethe container. This forms Specific Embodiment 19. In the container ofSpecific Embodiment 19, it was possible to form a light color DLC filmon the container neck portion in the same way as in Specific Embodiment17. It was possible to manufacture a container having a light uniformcolor over the entire container while ensuring an oxygen barrierproperty. Further, the same results were obtained even by the apparatusin which the container side electrode in the apparatus of FIG. 3 isformed as a similar shaped electrode.

A container was manufactured in accordance with Manufacturing Method 2using the manufacturing apparatus in the case where a tube made offluororesin is used as the source gas inlet pipe 9 in the apparatusshown in FIG. 3 in which the mouth side electrode 5 is arranged outsidethe container. This forms Specific Embodiment 20. In the container ofSpecific Embodiment 20, it was possible to form a light color DLC filmon the container neck portion in the same way as in Specific Embodiment17. It was possible to manufacture a container having a light uniformcolor over the entire container while ensuring an oxygen barrierproperty. Further, the same results were obtained even by the apparatusin which the container side electrode in the apparatus of FIG. 3 isformed as a similar shaped electrode.

A container was coated with a DLC film to form Specific Embodiment 21 inaccordance with the conditions described in Manufacturing Method 2 bythe manufacturing apparatus shown in FIG. 12 in which a so-calledsimilar shaped electrode is arranged. Further, a container was coatedwith a DLC film to form Specific Embodiment 22 in accordance with theconditions described in Manufacturing Method 3 by the manufacturingapparatus shown in FIG. 12 in which a so-called similar shaped electrodeis arranged. In the container of either Specific Embodiment 21 orSpecific Embodiment 22, it was possible to form a light color DLC filmon the container neck portion in the same way as in Specific Embodiment17. It was possible to manufacture a container having a light uniformcolor over the entire container while ensuring an oxygen barrierproperty. Further, the same results were obtained by the apparatus shownin FIG. 1.

A container was coated with a DLC film to form Comparative Example 3 inaccordance with the conditions described in Manufacturing Method 1 bythe manufacturing apparatus shown in FIG. 12 in which a so-calledsimilar shaped electrode is arranged. The container of ComparativeExample 3 had a film thickness (average for the entire container) of 27nm. The oxygen permeability was 0.0045 ml/container (500 ml PETcontainer)/day (23° C. and RH90%, measurement values after 20 hours fromthe start of nitrogen gas replacement), and the b* value was 9.2.Accordingly, the container secured an oxygen barrier property but hadirregular color that created coloration in the neck portion.

When specific embodiments 17˜22 and Comparative Example 3 are compared,Manufacturing Method 2 and Manufacturing Method 3 are manufacturingmethods which make it possible to manufacture a container having a lightuniform color over the entire container while securing an oxygen barrierproperty by reducing degradation due to plasma damage or plasma etchingof the DLC film at the neck portion even when applied to either theapparatus in the present invention or the prior art apparatus in which asimilar shaped electrode is arranged.

1-23. (canceled)
 24. A method of DLC film coating a plastic container,comprising: DLC film coating said container in an apparatus, whereinsaid apparatus comprises: a container side electrode which forms oneportion of a pressure-reducing chamber which houses a container formedfrom plastic in which the cross-sectional area of an opening of saidcontainer is smaller than the cross-sectional area of a horizontal crosssection at a body portion of said container and a neck portion isprovided between said opening and said body portion, and a facingelectrode which faces said container side electrode and is arrangedinside said container or above said opening, wherein said container sideelectrode and said facing electrode are made to face each other via aninsulating body which forms a portion of said pressure-reducing chamber,source gas supply means which supply a source gas that is converted toplasma for coating the inner wall surface of said container with adiamond like carbon (DLC) film includes a supply gas inlet pipe providedin said pressure-reducing chamber to introduce said source gas suppliedto said pressure-reducing chamber to the inside of said container,exhaust means which exhaust gas inside said pressure-reducing chamberfrom above the opening of said container are provided, and highfrequency supply means which supply a high frequency is connected tosaid container side electrode; wherein said container side electrode isformed so that the average inner hole diameter (R2) of the inner wallsurrounding said neck portion is smaller than the average inner holediameter (R1) of the inner wall surrounding said body portion, and theaverage distance (d2) between the outer wall of said container and theinner wall of said container side electrode in a horizontal crosssection with respect to the vertical direction of said container at saidneck portion becomes longer than the average distance (d1) between theouter wall of said container and the inner wall of said container sideelectrode in a horizontal cross section with respect to the verticaldirection of said container at said body portion.
 25. The method ofclaim 24, wherein said average distance d2 is formed to be a distancewhich suppresses the rise in plasma density accompanying the rise inpressure of the source gas converted to plasma at said neck portioninside said container in order to form a roughly uniform plasma densityinside said container.
 26. The method of claim 24, wherein said averagedistance d2 is formed to be the same as or shorter than the distance atwhich the strength of ionic impacts due to collisions of the ions of thesource gas converted to plasma with the inner wall surface of saidcontainer forms an ionic impact strength capable of forming a DLC filmhaving a prescribed lower limit oxygen barrier property, and saidaverage distance d2 is formed to be the same as or longer than thedistance at which the entire wall surface of said container has aroughly uniform color by suppressing coloration of a specific part ofsaid container from said neck portion to said opening caused by plasmadamage or plasma etching of the inner wall surface of said container dueto the increase in plasma density accompanying the increase in pressureof the source gas converted to plasma in said neck portion inside saidcontainer.
 27. The method of claim 24, wherein said average distance d2is formed to be a distance at which the DLC film coated plasticcontainer secures a prescribed oxygen barrier property and the entirewall surface of said DLC film coated plastic container has a roughlyuniform color.
 28. The method of claim 24, wherein the average diameterof said body portion of said container is made D1, the average diameterof said neck portion is made D2, and in the case where K is made anoffset coefficient that satisfies the relationship of Equation 1, theoffset coefficient K satisfies the relationship of Equation 2 orEquation 3, and said average distance d2 forms the d2 determined fromEquation 1:d2=K×(D1−D2)/2+d1  Equation 10.29≦K≦0.79 where 0.2 mm≦d1≦2.0 mm Equation 20.11≦K≦0.51 where 2.0 mm<d1≦4.0 mm.  Equation 3
 29. The method of claim24, wherein the average diameter of said body portion of said containeris made D1, the average diameter of said neck portion is made D2, anoffset coefficient that satisfies the relationship of Equation 4 is madeK, and when a of Equation 4 is a container compensation coefficient thattakes into account the container shape dependency satisfying Equation 5,the offset coefficient K satisfies the relationship of Equation 2 orEquation 3, and said average distance d2 forms the d2 determined fromEquation 4:0.29≦K≦0.79 where 0.2 mm≦d1≦2.0 mm  Equation 20.11≦K≦0.51 where 2.0 mm<d1≦4.0 mm  Equation 3d2=αK×(D1−D2)/2+d1  Equation 4α=(D1/D2)²/3.54.  Equation 5
 30. The method of claim 24, wherein saidcontainer has an axial symmetrical shape with respect to the centralaxis of the vertical direction, and the inner wall shape of saidcontainer side electrode is formed to be an axial symmetrical shape withrespect to said central axis when said container is housed.
 31. Themethod of claim 24, wherein when said container is housed in saidcontainer side electrode, the inner wall of said container sideelectrode surrounding said body portion of said container is formed tohave a cylindrical shape, the inner wall of said container sideelectrode surrounding said neck portion of said container is formed tohave a truncated cone shaped cylindrical shape in which the diameterbecomes smaller toward the container opening, and the inner wall of saidcontainer side electrode is formed to have a continuous shape.
 32. Themethod of claim 31, wherein the inner wall of said container sideelectrode surrounding the opening of said container is formed to have acylindrical shape.
 33. The method of claim 24, wherein said body portionof said container has a square tube shape, the inner wall of saidcontainer side electrode surrounding said body portion of said containeris formed to have a square tube shape, the inner wall of said containerside electrode surrounding said neck portion of said container is formedto have a truncated pyramid shaped square tube shape in which thediameter becomes smaller toward the container opening, a square tubeshape or a shape which is a combination of these, and the inner wall ofsaid container side electrode is formed to have a continuous shape. 34.The method of claim 33, wherein the inner wall of said container sideelectrode surrounding the opening of said container is formed to have asquare tube shape.
 35. The method of claim 24, wherein said containerside electrode is formed so that d1 is greater than 0 mm and less thanor equal to 4 mm.
 36. The method of claim 24, wherein said container isa container for beverages.